Application of Travel Time Data and Statistics to Travel Time Reliability Analyses: Handbook and Support Materials
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U.S. Department of Transportation
Federal Highway Administration
Office of Operations
1200 New Jersey Avenue, SE
Washington, DC 20590
https://ops.fhwa.dot.gov/
FHWA-HOP-21-058
July 2023
Table of Contents
[ Foreword ] | [ Notice and Quality Assurance Statement ] | [ Technical Report Documentation ] | [ SI Modern Metric Conversion Factors ] | [ List of Acronyms ]
Chapter 1. Introduction
Task Purpose
Issues Surrounding Reliability
Trip-Based Travel Time Reliability
Standard Processing Procedures
Chapter 2. Data Sources for Reliability
Freeway Detectors
Traffic Signal Detectors
Vehicle Re-Identification Technologies: Bluetooth®, Electronic License Plate Readers, and Toll Tag Readers
Vehicle Probe Data from Commercial Sources
Ride-Hailing Companies
Connected Vehicles
Summary of Travel Time Data Sources
Travel Time Data Used in this Study
Chapter 3. Data Processing for Reliability
Setting Spatial and Temporal Scales
Travel Time Calculation Methods
Step 1: Combine Lane Data into Station Data
Step 2: Calculate Link Statistics
Step 3: Calculate Section Statistics
Analysis Procedures
Data Extraction
Data Transformation
Data Aggregation
Measures Calculation
Chapter 4. Case Study: Developing and Comparing Reliability Measures Using Different Sources and Analytic Methods
Analysis Framework
Results
Speed and Travel Time Distributions
PTI Results by Data Source/Method
Relationships Between Measures by Data Source/Method
Examining Reliability Definitions: PTI versus PM3 System Reliability
Chapter 5. Conclusions
Data Sources for Travel Time Reliability
Results of the Case Study
Appendix A. Steps and Python Code for Reliability Data Processing
Data Processing for Reliability
Data Extraction and QC
Spatial and Temporal Aggregation: Development of the Travel Time Distribution
Creating Reliability Measures: Step-by-Step Calculation
List of Figures
Figure 1. Graph. Example travel time distribution and associated reliability measures.
Figure 2. Flow chart. Performance measure analysis workflow.
Figure 3. Diagram. Aftermarket safety device event and breadcrumb data collection and processing sequence.
Figure 4. Flow chart. Creating segment (facility) travel times.
Figure 5. Equation. Formula for mean absolute deviation.
Figure 6. Equation. Formula for identifying errors.
Figure 7. Equation. Formula for computing free-flow speed on signalized highways.
Figure 8. Equation. Formula for calculating delay per signal.
Figure 9. Line graph. Speed distribution—CA I-5 northbound 2017.
Figure 10. Line graph. Travel time distribution—CA I-5 northbound 2017.
Figure 11. Line graph. Speed distribution—CA I-5 southbound 2017.
Figure 12. Line graph. Travel time distribution—CA I-5 southbound 2017.
Figure 13. Line graph. Speed distribution—MD I-695 northbound 2018.
Figure 14. Line graph. Travel time distribution—MD I-695 northbound 2018.
Figure 15. Line graph. Speed distribution—MD I-695 southbound 2018.
Figure 16. Line graph. Travel time distribution—MD I-695 southbound 2018.
Figure 17. Line graph. Speed distribution—MD I-495 and Georgia Avenue eastbound 2018.
Figure 18. Line graph. Travel time distribution—MD I-495 and Georgia Avenue eastbound 2018.
Figure 19. Line graph. Speed distribution—MD I-495 and Georgia Avenue westbound 2018.
Figure 20. Line graph. Speed distribution—MD I-495 and Georgia Avenue westbound 2018.
Figure 21. Line graph. Speed distribution—TN I-40/I-75 eastbound 2018.
Figure 22. Line graph. Travel time distribution—TN I-40/I-75 eastbound 2018.
Figure 23. Line graph. Speed distribution—TN I-40/I-75 westbound 2018.
Figure 24. Line graph. Travel distribution—TN I-40/I-75 westbound 2018.
Figure 25. Scatterplot. Facility planning time index by data/method—a.m.
Figure 26. Scatterplot. Facility planning time index by data/method—p.m.
Figure 27. Bar graph. Difference in planning time index values by method, continuous trips throughout the year.
Figure 28. Line graph. Percent difference in planning time index values for continuous trips throughout the year.
Figure 29. Scatterplot. Planning time index values by computation method for discrete trip start times.
Figure 30. Scatterplot. Percent difference in planning time index values for different methods, discrete trip start times.
Figure 31. Graph. Relationship between Performance Measure Rule 3 System Reliability and planning time index, Northern Virginia Interstates.
Figure 32. Graph. Relationship between Performance Measure Rule 3 System Reliability and planning time index, Los Angeles and San Francisco freeways.
Figure 33. Graph. Relationship between Performance Measure Rule 3 System Reliability and planning time index, signalized arterials in several States.
Figure 34. Screenshot. Code for reading National Performance Management Research Data Set data.
Figure 35. Screenshot. Code for reading traffic message channel data.
Figure 36. Screenshot. Code for reading traffic message channel definition data.
Figure 37. Screenshot. Code for creating the data template.
Figure 38. Screenshot. Code for Reading Merging traffic message channel and Travel Time Data.
Figure 39. Screenshot. Code for data quality control check.
Figure 40. Screenshot. Code for creating additional temporal variables.
Figure 41. Screenshot. Code for calculating section travel time data.
Figure 42. Screenshot. Code for creating travel times using the virtual probe method.
Figure 43. Screenshot. Code aggregating travel times to the section level.
Figure 44. Screenshot. Code for aggregating travel time data to different temporal levels.
Figure 45. Screenshot. Code for creating free-flow speeds and travel times as well as the planning time index from aggregated travel time data.
Figure 46. Screenshot. Code for creating the 80th percentile travel time index measure.
Figure 47. Screenshot. Code for creating the mean travel time index.
Figure 48. Screenshot. Code for creating the semistandard deviation.
Figure 49. Screenshot. Code for creating the percent of trips operating at different speed thresholds.
Figure 50. Screenshot. Code for creating level of travel time reliability metric (step 1).
Figure 51. Screenshot. Code for creating level of travel time reliability metric (step 2).
Figure 52. Screenshot. Code for creating level of travel time reliability metric (step 3).
Figure 53. Screenshot. Code for creating system reliability measure.
List of Tables
Table 1. Validity criteria for freeway detector data.
Table 2. Basic safety message core data fields.
Table 3. Crumb data fields.
Table 4. Characteristics of travel time data sources used for reliability analysis.
Table 5. National Performance Management Research Data Set data sample, 2017.
Table 6. Detector data sample—California Department of Transportation performance measurement system, 2017.
Table 7. Trajectory data sample, 2018.
Table 8. Selected reliability performance measures derived from the travel time distribution.
Table 9. Case study analysis plan.
